This invention pertains generally to technology for sensing and measuring electromagnetic radiation (photons) using scintillator devices. More particularly, the invention pertains to a configuration of scintillation material, shielding, and radiation source that may be used to measure properties of material in or around a wellbore (borehole). For example, the invention may be used to efficiently measure the density of fluid in the borehole when deployed in a wireline or other logging tool.
Prior-art systems for the measurement of fluid density in producing oil and gas wells are based on a sensor with a radio-isotope source such as 241Am. Radiation from the source traverses the borehole fluid in an open sample cell and the counts received by a detector on the opposing end of the sample cell are dependent on the fluid density. In these prior-art systems the use of radio-isotopes cause concerns for health and safety of personnel and security of radio-isotopes.
Miniature x-ray tubes are viable alternate radiation sources if the output of the tube can be accurately measured. In laboratory and industrial applications, a separate output-monitor detector is added to monitor tube output. Use of a separate output-monitor detector for in situ measurements in a borehole is problematic due to space constraints that constrain sensors to a small diameter and long aspect.